Nintendo wasn't able to offer a date for when the patch will be available, but it says it will be available soon. In the meantime, Nintendo is recommending that players DO NOT save in the areas highlighted in blue in the map of Lumiose City above.

Nintendo has sold more than four million copies of Pokémon X & Y since its launch. That's a lot of games that will need a patch.

Our TakeNintendo has a pretty stellar track-record when it comes to releasing bug-free games. It's a testament to their skill when we say that the appearance of this bug is a surprise. Hopefully the patch will be available soon.

It's a good thing that Nintendo is aware of this. Right now, every time i'm in Lumoise City in the game and want to save, I always go to some other town first just in case. Hopefully, this fix will release within the next few days or possibly a week.

I personally haven't had a problem with this, but that's because I haven't tried to save in lumiose city. There's not really anything in there for me to go to anyway, besides the part where you have to meet the professor.